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Help on modifying mineral phase in thermo database


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Hi all,

I need a help to modify a mineral phase in thermo database.

I have this one:


Chabazite type= silica

formula= CaAl2Si4O12:6H2O

mole vol.= 200.202 cc mole wt.= 506.4690 g

5 species in reaction

-8.000 H+ 1.000 Ca++ 4.000 SiO2(aq)

2.000 Al+++ 10.000 H2O

-3.3630 -3.0810 -2.7573 -2.4617

-2.1708 -1.9414 -1.7559 -1.6027


but I need to insert a specific kind of chabazite with the following chemical formula:




I'm not too much practiced with chemical balance and free Gibbs energy so anyone can help me?


Thanks for every help

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Hi Sosfa,


You'll need to search the literature for a reaction between Chabazite and some form of K, Ca, Al, Si, O, and H species. You'll need an equilibrium constant for the reaction, or some way to calculate the equilibrium constant, perhaps from free energies of formation of each species in the reaction.


Hope this helps,


Brian Farrell

Aqueous Solutions LLC

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hi all, i'm working on thermo database


my mineral phase is now


Chabazite type= silica
formula= K2CaAl4Si8O24:10H2O
mole vol.= 200.202 cc mole wt.= 506.4690 g
6 species in reaction
-24.000 H+ 1.000 Ca++ 8.000 SiO2(aq)
2.000 K+ 4.000 Al+++ 18.000 H2O


but when act2 opens gives me an error

"reaction charge imbalance for chabazite = -4"


can someone help me in balancing the reaction?


I'm not too much expert


thank you guys

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Hi Sosfa,


It looks like the number of H+ on the left-hand side (LHS) of the reaction is wrong. Since you have 18 H2O's on the right-hand side (RHS), you'll need 36 H's on the LHS. There are already 20 H's on the LHS from Chabazite, so you only need 16 more H's as H+. Once you change that, your reaction should be balanced in terms of mass and charge.


Don't forget, you'll need to specify the equilibrium constants (log Ks) at each of the 8 principal temperatures of the thermo dataset. If you don't know the value for a particular temperature, you can simply set the log K to 500.


Hope this helps,


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